What benefit is provided by column filtering?
A.
The Exadata Storage Server can select rows based on column values listed in a SQL predicate
B.
Storage indexes are built on columns for use in filtering
C.
Only necessary columns are returned to the database server
D.
Column filtering is a marketing term, not a real benefit
Explanation:
Exadata provides column filtering, also called column projection, for table scans.
Only the
columns requested are returned to the database server rather than all columns in a table.
For example, when the following SQL is issued, only the employee_name and employee_number
columns are returned from Exadata to the database kernel.SELECT employee_name, employee_number FROM employee_table;
For tables with many columns, or columns containing LOBs (Large Objects), the I/O bandwidth
saved can be very large. When used together, predicate and column filtering dramatically
improves performance and reduces I/O bandwidth consumption. In addition, column filtering
also applies to indexes, allowing for even faster query performance.
Reference: http://www.oracle.com/technetwork/database/exadata/exadata-technical-whitepaper-134575.pdf